Reborn in 1984, fishing and hunting in Jiangnan

Chapter 58

In mid-May, the water temperature of Baiyang Lake rose to 24 degrees Celsius.

Ma Yuanchao and Qin Shulan stood beside the water trough, wearing high-top rain boots, at the edge of the circular seedling pond.

They are putting two wild mandarin fish broodstock caught from Baiyang Lake into the spawning pool.

Both parent fish were selected; the female's belly was swollen, her vent was red and swollen, and her gonads were fully developed.

The male fish has a slender body and a fine layer of tubercles on its gill covers.

That's a sign of sexual maturity.

"The key to artificially inducing spawning in mandarin fish is two injections."

Ma Yuanchao took two syringes out of the incubator; the needles were as thin as a hair.

"The first injection was around 9 a.m., an injection of oxytocin No. 1, at a dosage of 0.5 ml per kilogram of body weight, injected at the base of the dorsal fin."

"Its function is to induce synchronous maturation of follicles."

"The second injection will be at 4 PM, an injection of oxytocin No. 2, at a dose of one milliliter per kilogram, injected at the same site."

"Its function is to stimulate ovulation."

Qin Shulan opened the experiment record book and wrote down the date, water temperature, parent fish weight, and injection dosage.

She looked up at Chen Zheng and said, "The water temperature between the two injections is crucial."

"The water temperature must be kept stable between 24 and 26 degrees Celsius."

"Below 23 degrees Celsius, the labor-inducing effect is halved."

"Above 27 degrees Celsius, the eggs become over-mature, and the fertilization rate drops significantly."

"The shade netting around the seedling pond should be adjusted frequently to maintain a stable water temperature."

Chen Zheng readjusted the position of the shade net and then used a thermometer to measure the water temperature.

Twenty-four and a half degrees, just right.

Ma Yuanchao scooped the two parent fish out of the spawning pool and wrapped their heads with a wet towel.

Qin Shulan took the syringe, inserted the needle into the base of the dorsal fin, and slowly injected the solution.

The parent fish twisted slightly, then quieted down again.

After the injection was completed, the two put the parent fish back into the spawning tank, turned on the circulating water pump, and let the water flow slowly over the fish's body.

"From now on, you will take turns monitoring the water temperature changes and fill in the form every hour."

"If the temperature drops significantly at night, use a constant temperature heater to regulate it, and make sure the temperature difference does not exceed two degrees."

Qin Shulan then handed several handwritten experimental record sheets to Chen Zheng.

Water temperature records, parent fish condition, water quality changes, spawning time, fertilized egg count, and hatching time of fry—each item must be filled out carefully.

She said that good experimental records are a form of technical accumulation, and that complete data will help others avoid detours in the future.

This experiment lasted for nearly twenty hours.

At four o'clock the next morning, the water temperature stabilized at twenty-five degrees, and the female fish began to lay eggs.

Stimulated by ovulation, the male fish circles around the female fish, continuously releasing sperm.

A layer of pale yellow foam rose to the surface of the water.

Ma Yuanchao shone his flashlight into the water and saw a dense layer of transparent fish eggs on the bottom. Each egg had a small black dot in the center, which was the developing embryo.

"The fertilization rate is good, estimated to be over 60%."

Ma Yuanchao straightened up, and a relaxed expression finally appeared on his face.

"For artificial breeding of mandarin fish, a fertilization rate of over 60% is considered half the battle won."

"The most crucial step next is incubation."

"Mandarin fish eggs are semi-buoyant, so the water flow cannot be stopped."

"Once the eggs stop laying, they sink to the bottom, and once they sink, they suffocate."

"The water flow in the circular pool must be kept constant, the water pumps must run 24 hours a day, and a dedicated person must be on duty in the pump room, ready to switch to the standby pump at any time."

Qin Shulan squatted by the sink with a magnifying glass in hand, counting the eggs while taking notes in her notebook.

After counting them once, I counted them a second time to confirm that there were approximately 10,000 grains.

She looked up and said that with a 60% fertilization rate, if these eggs can hatch successfully, there will be about 5,000 fry.

However, the two weeks from hatching to stocking the pond are the most difficult to manage for mandarin fish fry. They need plenty of feed for the first few days, and then you have to start sorting them by size, otherwise the larger ones will bite the smaller ones.

Chen Zheng wrote these words down in his notebook.

The fish eggs incubated in the circular pool for two days and two nights.

On the morning of the third day, while he was squatting by the seedling pond to observe, he noticed very subtle movements beneath the surface of the water.

Several translucent fish fry are emerging from the egg membrane. They are only three or four millimeters long, not much thicker than a human hair.

As soon as they hatch, they lie on their backs, relying on the yolk sac inside their bodies to maintain their initial nutrition.

Two more days passed, and more and more fish fry hatched, numbering around four or five thousand.

Chen Zheng and Li Quan took turns guarding the pool, changing the rotifer culture medium every four hours.

The few buckets of rotifer algae seedlings left behind by Ma Yuanchao before he left came in very handy. Rotifers reproduce quickly, doubling in number every day, which was just enough to keep up with the fish fry's feeding density.

The fish fry began to feed on rotifers in large quantities from the fourth day.

Their digestive tracts are transparent, and you can see clumps of green inside their stomachs through their bodies.

That's the color of the rotifer after it's been swallowed and digested in the stomach.

Chen Zheng used a magnifying glass to observe the fish fry's feeding behavior and only felt relieved after confirming that they had begun to actively eat live bait.

The second batch of mandarin fish spawning experiments was conducted at the end of May.

This time, the parent fish were in better condition, the water temperature was higher and more stable, and the fertilization rate reached over 70%.

After two rounds of experiments, the total number of mandarin fish fry in the circular nursery pond exceeded 8,000.

Although these fish fry still need a two-month frying period to grow into three- or four-inch juveniles, and the survival rate will not be very high, this is the first time that artificial breeding of mandarin fish has been achieved in the Baiyang Lake area.

The news quickly spread to the county and the province.

After listening to Ma Yuanchao's report over the phone, the leaders of the Provincial Fisheries Research Institute immediately approved adding 3,000 yuan to the experimental funding.

Ma Yuanchao relayed to Chen Zheng over the phone that the newly allocated funds could be used to purchase constant temperature equipment and aerators, and starting next year, mandarin fish fry would be artificially bred and hatched locally at the Baiyang Town Promotion Station, no longer relying on the provincial institute to send parent fish for guidance.

In early June, Chen Zheng received a notification from the county agricultural bureau that the matching loan for the Baiyang Town extension station had been approved.

The loan, totaling 2,200 yuan, is for supporting water conservancy facilities used to expand and renovate a three-tiered fishpond. The interest rate is half that of ordinary agricultural loans, and the repayment period has been extended to five years.

Adding the remaining loan balance from the demonstration households and the money saved from selling mountain products in the winter, the promotion station has about 4,500 yuan in funds available in its accounts.

When Chen Zheng received the news of the loan, he was in the yard replacing the motor belt of the aerator.

He put down the wrench, read the notification form twice from beginning to end, then rode the bicycle he had borrowed countless times to the Agricultural Bank branch in town and activated the loan account.

The round-faced girl at the counter saw the long string of numbers on his bankbook, glanced up at him, then looked down again to count the zeros, a slight smile playing on her lips.

That evening, Chen Zheng invited Chen Laosan to the edge of the fishpond.

In the fishpond, the impellers of the aerators were splashing water, and the white shadows of silver carp and bighead carp turning over could be seen from time to time beneath the surface.

The water pumps on the other side of the circular pool were humming.

He pointed to the newly repaired No. 3 pond dam foundation and told Chen Laosan.

The next step is to expand the water surface here by another acre and build an independent turtle breeding pond.

He then pointed to the row of brick and tile houses at the end of the pond embankment and said that the town's promotion station already had a duty room for rotating shifts.

I plan to install another public telephone at the station in a few months.

Old Chen, with his pipe in his mouth, slowly walked around the pond embankment.

Finally, he squatted down by the circular pool and looked at the clear stream of water flowing from the pump outlet.

He only said one word.

"it is good."